When a semiconductor switching device (e.g., an insulating gate bipolar transistor) operates in a normally ON state, a collector-emitter voltage is held in a state where the collector-emitter voltage is lowered to a saturation voltage of the semiconductor switching device. However, when the semiconductor switching device is short-circuited, the collector-emitter voltage rises from the saturation voltage due to an overcurrent. A state where the collector-emitter voltage rises to a voltage higher than the saturation voltage is also called “desaturation”, and the collector-emitter voltage obtained when the semiconductor switching device is in the desaturation state is also called a “desaturation voltage” or “DESAT voltage”.
As disclosed in, for example, JP H09-247951 A, a circuit device having a short-circuit protection function for a high-potential-side semiconductor switching device has been heretofore known. In JP H09-247951 A, a first resistor is provided between a drive circuit of a semiconductor device and a semiconductor switching device, and a second resistor is provided in the drive circuit. The first resistor is provided outside the drive circuit, and a voltage generated between the terminals of the semiconductor switching device is detected by a voltage that is divided by the first resistor and the second resistor provided in the drive circuit.